1. Field of the Invention
The present invention relates to a vehicle driving support apparatus, particularly the apparatus controls the vehicle to follow-up a leading vehicle detected by a stereo camera, a monocular camera, a millimeter wave radar, or the like, in front of an own vehicle
2. Description of the Related Art
In recent years, ACC system (Adaptive Cruise Control System) has been put to practical use. This system detects a traveling environment ahead of a vehicle with a camera or the like mounted on the vehicle and detects a leading vehicle from data of the traveling environment to perform follow-up traveling control for the leading vehicle and keep an intervehicular distance or the like between the vehicle and the leading vehicle at a predetermined distance or more.
For example, Japanese Patent unexamined publication 2002-127781 discloses a technique for calculating intervehicular time, which is a time difference until an own vehicle reaches a present position of a leading vehicle, on the basis of an intervehicular distance and own vehicle velocity and controlling an electronic throttle and a brake actuator in order to keep the intervehicular time at target intervehicular time (a fixed value) set in advance. In this case, when a magnitude of deceleration of the leading vehicle increases to a first defined value or more, a predetermined correction value is added to the target intervehicular time to obtain corrected intervehicular time. Acceleration and deceleration control is performed with the corrected intervehicular time set as a target.
Incidentally, a driver feels it more natural if the target intervehicular time set in the above publicaiton takes different values according to traveling states of the own vehicle. With the target intervehicular time of a fixed value in the above publication, even if the target intervehicular time is corrected when the leading vehicle decelerates, the driver, who is performing follow-up traveling, cannot perform follow-up traveling with natural and satisfactory feeling. On the other hand, with respect to follow-up control in control performed in a low speed range and control performed in a medium and high speed range, it is difficult to use target intervehicular time in common from the viewpoint of an intervehicular distance to be secured, a margin for time, and the like. The difference of target intervehicular time gives the driver an unnatural feeling at a boundary of the low speed range and the medium and high speed range.